1 00:00:00,520 --> 00:00:03,800 Speaker 1: Welcome to Brainstuff from how stuff works dot com where 2 00:00:03,840 --> 00:00:15,640 Speaker 1: smart Happens. Hi Marshall Brain with today's question, how do 3 00:00:15,920 --> 00:00:20,080 Speaker 1: the new gasoline direct injection engines work and what are 4 00:00:20,120 --> 00:00:26,000 Speaker 1: the advantages? Think about the internal combustion gasoline engine. We 5 00:00:26,120 --> 00:00:29,600 Speaker 1: have a love hate relationship with it. It creates a 6 00:00:29,640 --> 00:00:34,160 Speaker 1: lot of pollution, It's incredibly inefficient, It spews carbon into 7 00:00:34,240 --> 00:00:37,519 Speaker 1: the atmosphere. It makes us dependent on crude oil, with 8 00:00:37,600 --> 00:00:41,840 Speaker 1: negative side effects like oil spills and trade imbalances. Yet 9 00:00:41,880 --> 00:00:46,640 Speaker 1: we're completely dependent on the internal combustion engine. Nearly every 10 00:00:46,680 --> 00:00:49,879 Speaker 1: car on the road today in America has one, and 11 00:00:49,920 --> 00:00:52,440 Speaker 1: they will be with us for some time to come. 12 00:00:52,840 --> 00:00:56,640 Speaker 1: Have you ever wondered why? There are four things about 13 00:00:56,680 --> 00:00:59,480 Speaker 1: the internal combustion engine that make it the engine of 14 00:00:59,600 --> 00:01:03,200 Speaker 1: choice in the vast majority of our cars. First, and 15 00:01:03,240 --> 00:01:07,200 Speaker 1: probably most importantly, it is reliable. A typical engine will 16 00:01:07,280 --> 00:01:09,959 Speaker 1: last at least a hundred thousand miles if you take 17 00:01:09,959 --> 00:01:12,160 Speaker 1: care of it, and it will do its job in 18 00:01:12,240 --> 00:01:17,480 Speaker 1: the hottest deserts and the coldest winters. Second, relatively speaking, 19 00:01:17,600 --> 00:01:20,720 Speaker 1: it doesn't weigh much for the power it produces. An 20 00:01:20,720 --> 00:01:23,839 Speaker 1: electric motor and its battery pack way a lot more. 21 00:01:24,560 --> 00:01:27,000 Speaker 1: The same could be said for the cost of the engine. 22 00:01:27,360 --> 00:01:31,680 Speaker 1: Batteries are really expensive right now. And finally, you can 23 00:01:31,720 --> 00:01:35,679 Speaker 1: recharge and internal combustion engine by filling the gas tank. 24 00:01:35,880 --> 00:01:38,880 Speaker 1: That process only takes a couple of minutes. For an 25 00:01:38,880 --> 00:01:42,199 Speaker 1: electric car, it takes hours and hours to recharge, making 26 00:01:42,200 --> 00:01:45,960 Speaker 1: it impractical for any kind of long road trip. If 27 00:01:46,000 --> 00:01:50,800 Speaker 1: we could invent cheap, light fast recharge batteries, the internal 28 00:01:50,800 --> 00:01:54,680 Speaker 1: combustion engine would die. If we can invent fuel cells 29 00:01:54,760 --> 00:01:58,520 Speaker 1: that are inexpensive and reliable, the internal combustion engine would die. 30 00:01:58,920 --> 00:02:01,760 Speaker 1: But right now there's nothing that comes close to the 31 00:02:01,800 --> 00:02:06,160 Speaker 1: internal combustion engine, even with all its problems. So car 32 00:02:06,240 --> 00:02:09,760 Speaker 1: manufacturers are trying to improve the internal combustion engine, a 33 00:02:09,840 --> 00:02:12,760 Speaker 1: process that's been going on for a hundred years, and 34 00:02:12,800 --> 00:02:18,560 Speaker 1: the latest incarnation is pretty remarkable. It's called gasoline direct injection, 35 00:02:18,680 --> 00:02:21,040 Speaker 1: and it should make it possible to get cars up 36 00:02:21,040 --> 00:02:24,600 Speaker 1: to seventy miles per gallon or so even before adding 37 00:02:24,639 --> 00:02:28,920 Speaker 1: a hybrid drive. Just about every major manufacturer will be 38 00:02:28,960 --> 00:02:33,320 Speaker 1: releasing some type of gasoline direct injection technology in two 39 00:02:33,320 --> 00:02:36,959 Speaker 1: thousand eleven. If you look across the claims from all 40 00:02:36,960 --> 00:02:40,280 Speaker 1: of the different companies, there are several common threads and 41 00:02:40,320 --> 00:02:44,040 Speaker 1: what they're doing. The engines all use a new type 42 00:02:44,040 --> 00:02:47,480 Speaker 1: of fuel injector that can spray fuel directly into the 43 00:02:47,560 --> 00:02:51,480 Speaker 1: cylinder during the compression stroke. To do that, they all 44 00:02:51,560 --> 00:02:55,320 Speaker 1: need extremely high pressure fuel pumps rated at something around 45 00:02:55,320 --> 00:02:59,239 Speaker 1: two thousand p s i in current cars. The fuel 46 00:02:59,240 --> 00:03:03,640 Speaker 1: injection technlogy being used is called port fuel injection, where 47 00:03:03,639 --> 00:03:07,800 Speaker 1: the injector sprays fuel at low pressure into the intake manifold. 48 00:03:08,480 --> 00:03:12,280 Speaker 1: The direct injection process allows the fuel to evaporate in 49 00:03:12,360 --> 00:03:16,040 Speaker 1: the cylinder and cool the air fuel mixture that helps 50 00:03:16,040 --> 00:03:21,040 Speaker 1: avoid premature ignition. So these engines can increase the compression ratio. 51 00:03:21,720 --> 00:03:25,440 Speaker 1: Mazda's new direct injection engine, for example, goes up to 52 00:03:25,520 --> 00:03:29,240 Speaker 1: a fourteen to one compression ratio, which has never been 53 00:03:29,280 --> 00:03:32,880 Speaker 1: seen before in a production gasoline engine. The normal high 54 00:03:32,880 --> 00:03:35,240 Speaker 1: has been twelve to one or so, and that would 55 00:03:35,240 --> 00:03:38,960 Speaker 1: require premium fuel in the past. Many of the engines 56 00:03:39,000 --> 00:03:44,160 Speaker 1: are using multiple injector sprays per stroke. One spray occurs 57 00:03:44,200 --> 00:03:47,200 Speaker 1: as the air starts flowing in on the intake stroke 58 00:03:47,280 --> 00:03:50,760 Speaker 1: to cool things down. The second occurs right before the 59 00:03:50,840 --> 00:03:54,520 Speaker 1: spark plug fires. This creates a stratified charge in the 60 00:03:54,560 --> 00:03:58,760 Speaker 1: cylinder for a better burn pattern using less fuel. The 61 00:03:58,840 --> 00:04:03,000 Speaker 1: high compression ratio also allows more energy to be extracted 62 00:04:03,000 --> 00:04:06,520 Speaker 1: from the gasoline. Think of it this way. When gasoline 63 00:04:06,600 --> 00:04:10,840 Speaker 1: burns in a higher compression environment, it gets to expand further, 64 00:04:11,120 --> 00:04:14,560 Speaker 1: meaning that more work can be extracted from that expansion. 65 00:04:15,040 --> 00:04:18,520 Speaker 1: The stratified charge allows less fuel to be injected while 66 00:04:18,640 --> 00:04:22,000 Speaker 1: still getting a good ignition and burn pattern. It allows 67 00:04:22,040 --> 00:04:25,600 Speaker 1: a much leaner mixture in the cylinder. One of the 68 00:04:25,720 --> 00:04:31,320 Speaker 1: key technologies making gasoline direct injection possible is new piezoelectric 69 00:04:31,480 --> 00:04:37,359 Speaker 1: fuel injectors. They're extremely precise and extremely fast. They also 70 00:04:37,440 --> 00:04:42,320 Speaker 1: provide an unexpected side effect In some cases. With these injectors, 71 00:04:42,360 --> 00:04:45,880 Speaker 1: it's possible to start a warm engine without using the 72 00:04:45,960 --> 00:04:49,680 Speaker 1: starter motor. The computer can find a cylinder that has 73 00:04:49,760 --> 00:04:53,360 Speaker 1: its piston in the right position, inject fuel, and fire 74 00:04:53,400 --> 00:04:57,240 Speaker 1: it to start the engine. This start stoppability should make 75 00:04:57,279 --> 00:05:00,800 Speaker 1: it easier for car manufacturers to create ours that no 76 00:05:00,839 --> 00:05:04,000 Speaker 1: longer need to idle at traffic lights, and that'll save 77 00:05:04,080 --> 00:05:08,279 Speaker 1: a lot of fuel while eliminating lots of urban pollutions. Again, 78 00:05:08,520 --> 00:05:12,839 Speaker 1: stop and go traffic for more illness, and thousands of 79 00:05:12,839 --> 00:05:15,440 Speaker 1: other topics does that how stuff works dot Com and 80 00:05:15,440 --> 00:05:17,400 Speaker 1: don't forget to check out the brain Stuff blog on 81 00:05:17,440 --> 00:05:19,640 Speaker 1: the how stuff works dot com home page. You can 82 00:05:19,680 --> 00:05:22,720 Speaker 1: also follow brain stuff on Facebook or Twitter at brain 83 00:05:22,760 --> 00:05:23,880 Speaker 1: stuff hs W